Field of the Invention
The present invention relates to an illumination optical apparatus and a device manufacturing method.
Description of the Related Art
Projection exposure apparatuses for manufacturing devices such as semiconductor devices or the like transfer a pattern formed on an original (mask, reticle or the like) onto a substrate (a wafer or the like where the surface thereof is coated with a resist layer) via an image formation optical system, a projection optical system, or the like. An exposure apparatus includes an illumination optical apparatus that illuminates an original with a beam of light from a light source. If illumination light emitting from an illumination optical apparatus to an original is not uniform or the telecentricity (the parallelism of the optical axis and principal rays) is lost, pattern transfer to a substrate becomes insufficient, so that the exposure apparatus cannot provide high quality devices. Thus, in order to form micro patterns on a substrate, illuminance uniformity on a surface to be illuminated such as a mask plane (reticle plane), a wafer plane, or the like needs to be improved. Hence, illumination optical apparatuses each provided with a rod-type optical integrator are known as a method for improving illuminance uniformity.
With the use of the above rod-type optical integrator, illumination light, illumination light emitted from the secondary light source, which has been formed corresponding to the number of times of internal reflections within the rod, is superimposed at the light-emitting end of the rod, so that the light intensity distribution at the light-emitting end surface of the rod can be uniformed. However, in the above-described illumination optical apparatus, the non-uniformity of the illuminance distribution on the surface to be illuminated may be observed due to various factors such as contamination of an optical system, eccentricity, unevenness of antireflective coating, or the like.
Accordingly, as a method for adjusting an illuminance distribution on a surface to be illuminated, an illumination optical apparatus as shown in Japanese Patent Laid-Open No. 2000-269114 is disclosed. The illumination optical apparatus disclosed in Japanese Patent Laid-Open No. 2000-269114 is provided such that the light amount controlling unit having a plurality of filter patterns which are provided in correspondence with secondary light source images is provided at a position on the incidence side of the rod-type optical integrator which is in an optically conjugated relationship with the light-emitting end surface of the rod-type optical integrator. In this manner, the state of light supplied from the secondary light source images to the surface to be illuminated is controlled, so that the illuminance distribution on the surface to be illuminated can be adjusted to a desired state.
However, in the illumination optical apparatus disclosed in Japanese Patent Laid-Open No. 2000-269114, if an arbitrary selection is made on positions at which filter patterns are disposed, the illuminance distribution on the surface to be illuminated may be non-uniform in the case where an attachment position error of the light amount controlling unit or a manufacturing position error of the filter pattern occurs. Furthermore, the telecentricity of illumination light for illuminating the surface to be illuminated may undesirably change.